The present invention relates to check valves and particularly to poppet type check valves such as are typically employed in pneumatic brake control valve devices for railroad vehicles.
Poppet type check valves generally comprise a valve element that moves perpendicularly relative to a seat to open and close a fluid conducting passageway in which the valve element and seat are situated. When used as a backflow check, the valve element is arranged to disengage its valve seat in response to fluid flow in a desired direction and to engage its valve seat in response to fluid flow in the opposite direction. Alternatively, a piston actuator may be employed to operate the check valve element in a direction to engage or disengage its valve seat.
One such poppet type check valve known in the prior art is shown in FIGS. 1 and 2 of the drawings and is commonly employed in the aforementioned pneumatic brake control valve devices. The valve element A of such poppet type check valves is typically made from a rubber compound that is bonded during a molding process to a stamped metal insert B to form a unitary structure. The metal insert gives rigidity to the rubber valve element and provides a fluted guide C that is adapted to engage the passageway in which the check valve is disposed. The flutes are designed to permit fluid to pass around the solid molded structure and to maintain proper alignment of the valve element with its seat.
In the manufacture of these insert-molded, unitary poppet type check valves, difficulty is encountered not only in the molding process itself, but also in the after-molding process of removing flashing produced during the molding operation. In addition, such a unitary valve structure requires replacement of the entire check valve, including the metal insert, when the rubber valve element becomes worn.